No growth disturbance after trochleoplasty for recurrent patellar dislocation in adolescents with open growth plates

AIMS AND OBJECTIVES: Trochlear dysplasia is the most important risk factor to patellofemoral instability in adolescents, therefore trochleoplasty to reshape the trochlear groove is the treatment of choice in patients with severe trochlear dysplasia. However, in the presence of open growth plates there is a potential risk of injury of the distal femoral growth plate and subsequent growth disturbance. Therefore, most authors do not recommend trochleoplasty in skeletally immature patients. The effect of trochleoplasty on femoral growth when performed before closure of the distal femoral physis remains unclear. The hypothesis of the study was, that In patients with open growth plates and an expected growth of less than two years trochleoplasty does not cause growth disturbance of the distal femur. MATERIALS AND METHODS: 18 consecutive adolescents (18 knees) with open physes and severe trochlear dysplasia underwent trochleoplasty. Pre- and postoperative radiographic examination included AP and lateral views to assess leg axis and patella alta. Preoperatively a radiograph of the left hand was performed to measure skeletal age. MRI was performed to evaluate trochlear dysplasia and tibial tubercle-trochlear groove (TT-TG) distance. Evaluation included pre- and postoperative physical examination with evaluation of leg length and leg axis, Kujala score, Activity Rating Scale (ARS) and Tegner activity score. RESULTS: The average age at the time of operation was 12.6 y (range, 12.2 - 13.3) in girls and 14.5 y (14.0 - 15.4) in boys. The average follow-up after operation was 2.3 years after surgery (range, 2.0 - 3.0 years). At follow-up in all patients the growth plates of the knee were closed. Impairment of growth of the distal femur was neither found clinically nor radiographically. No recurrent dislocation occurred. The median Kujala score and median VAS showed significant improvement (p < 0.01). The activity level according to the Tegner activity score did not change statistically significant. CONCLUSION: In this study, trochleoplasty as a treatment for patellofemoral instability in patients with open physes and an expected growth of not more than two years showed good clinical results without redislocation and no growth disturbance. Therefore, in selected adolescent patients with severe trochlear dysplasia trochleoplasty can be safely performed up to two years before the projected end of growth.